Engineering hard ferrite composites by combining nanostructuring and Al3+ Substitution: From nano to dense bulk magnets
Abstract
We have investigated the bottom-up sol-gel synthesis of nanocomposite powders comprising two magnetic phases (hexagonal Sr ferrite and spinel Co ferrite) in order to outline a strategy to obtain permanent magnets with large coercivities via low-cost and scalable syntheses. The correlation between morphological, structural and macroscopic magnetic properties of Al-substituted SrFe 12 O 19 and SrFe 12 O 19 /CoFe 2 O 4 nanocomposites was analyzed in detail. The hysteretic behavior can be tuned by cation substitution and/or modulation of the super-exchange coupling at the interface of the constituting phases. The magnetic data, supported by Monte Carlo simulations, indicates enhanced magnetic coupling within the composite: this observation underscores the significance of soft crystallite size and epitaxial growth quality at the interface as key factors influencing super-exchange coupling strength, ranging from fully coupled to essentially decoupled composites. Bulk magnets with high density were manufactured by compacting these nanostructured phases using spark plasma sintering, without an applied magnetic field. Consolidation of powders significantly impacted magnetic properties, by increasing remanent magnetization and decreasing coercivity due to enhanced super-exchange coupling. The presence of two phases hindered reciprocal growth, influencing coercivity differently in various compositions. Overall, the compaction enhanced magnet performance through improved particle alignment and super-exchange coupling, offering the potential for optimized magnet design.
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BibTeX
@article{maltoni2026engineering,
title = {{Engineering hard ferrite composites by combining nanostructuring and Al3+ Substitution: From nano to dense bulk magnets}},
author = {Pierfrancesco Maltoni and Gianni Barucca and Bogdan Rutkowski and Sergey Ivanov and Nader Yaacoub and Anastasiia Mikheenkova and Gustav Ek and Mirva Eriksson and Bjarne Almqvist and Marianna Vasilakaki and Gaspare Varvaro and Tapati Sarkar and José de Toro and Kalliopi Trohidou and Davide Peddis and Roland Mathieu},
journal = {Acta Materialia},
year = {2026},
month = sep,
doi = {10.1016/j.actamat.2024.120491},
url = {https://hal.science/hal-05747414v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Engineering hard ferrite composites by combining nanostructuring and Al3+ Substitution: From nano to dense bulk magnets
AU - Pierfrancesco Maltoni
AU - Gianni Barucca
AU - Bogdan Rutkowski
AU - Sergey Ivanov
AU - Nader Yaacoub
AU - Anastasiia Mikheenkova
AU - Gustav Ek
AU - Mirva Eriksson
AU - Bjarne Almqvist
AU - Marianna Vasilakaki
AU - Gaspare Varvaro
AU - Tapati Sarkar
AU - José de Toro
AU - Kalliopi Trohidou
AU - Davide Peddis
AU - Roland Mathieu
PY - 2026
DA - 2026/09/11
JO - Acta Materialia
DO - 10.1016/j.actamat.2024.120491
UR - https://hal.science/hal-05747414v1
AB - We have investigated the bottom-up sol-gel synthesis of nanocomposite powders comprising two magnetic phases (hexagonal Sr ferrite and spinel Co ferrite) in order to outline a strategy to obtain permanent magnets with large coercivities via low-cost and scalable syntheses. The correlation between morphological, structural and macroscopic magnetic properties of Al-substituted SrFe 12 O 19 and SrFe 12 O 19 /CoFe 2 O 4 nanocomposites was analyzed in detail. The hysteretic behavior can be tuned by cation substitution and/or modulation of the super-exchange coupling at the interface of the constituting phases. The magnetic data, supported by Monte Carlo simulations, indicates enhanced magnetic coupling within the composite: this observation underscores the significance of soft crystallite size and epitaxial growth quality at the interface as key factors influencing super-exchange coupling strength, ranging from fully coupled to essentially decoupled composites. Bulk magnets with high density were manufactured by compacting these nanostructured phases using spark plasma sintering, without an applied magnetic field. Consolidation of powders significantly impacted magnetic properties, by increasing remanent magnetization and decreasing coercivity due to enhanced super-exchange coupling. The presence of two phases hindered reciprocal growth, influencing coercivity differently in various compositions. Overall, the compaction enhanced magnet performance through improved particle alignment and super-exchange coupling, offering the potential for optimized magnet design.
SN - 1359-6454
ER -